When, in the foreclosure of a mortgage by advertisement, any sale of real property has been made after February 11, 1933, or shall be hereafter made by a mortgagee, trustee, or other person authorized to make the same pursuant to the power of sale contained therein, at which the mortgagee, payee or other holder of the obligation thereby secured has become or becomes the purchaser, or takes or has taken title thereto at such sale either directly or indirectly, and thereafter such mortgagee, payee or other holder of the secured obligation, as aforesaid, shall sue for and undertake to recover a deficiency judgment against the mortgagor, trustor or other maker of any such obligation, or any other person liable thereon, it shall be competent and lawful for the defendant against whom such deficiency judgment is sought to allege and show as matter of defense and set-off to the extent only of the amount of the plaintiff‘s claim, that the property sold was fairly worth the amount of the debt secured by it at the time and place of sale or that the amount bid was substantially less than its true value, and such showing shall constitute a defense to such action and shall defeat the deficiency judgment against him, either in whole or in part to such extent. This section shall not affect nor apply to the rights of other purchasers or of innocent third parties, nor shall it be held to affect or defeat the negotiability of any note, bond or other obligation secured by such mortgage, deed of trust or other instrument. Such proceedings, as aforesaid, shall in no way affect the title of the purchaser to the lands acquired by such purchase. This section shall not apply to foreclosure sales made pursuant to an order or decree of court nor to any judgment sought or rendered in any foreclosure suit nor to any chancery sale heretofore or hereafter made and confirmed.